Two things.
First, if you've connected your Sonoff to the Internet, you need to think about security. Otherwise you are totally open to some external bot network doing random things to your switch.
Secondly, if I remember rightly, the Maker channel is about events - I don't think the Sonof itself will do this. Rather you should use an intermediary such as Node-RED which does work really well and can trigger Maker events from MQTT very easily.